Meet the toxin that’s got Ontario corn farmers worried

Vomitoxin is exactly what it sounds like — and it’s turning up in corn throughout southwestern Ontario

David Bolton stands in front of his cornfield in Kerwood. (Mary Baxter)

KERWOOD — David Bolton’s corn crop is usually sitting in storage bins by now, but that’s not the case this year. Despite a personal-record yield, he’s left half of his 300-acre crop in the fields because, for the first time in 20 years, he doesn’t have a buyer.

He usually sells the corn to his next-door neighbour, a pig farmer, for livestock feed. But that’s not an option now, because the grain is contaminated with vomitoxin.

Hundreds of farmers in Middlesex and Huron counties and in Chatham-Kent have discovered the toxin in their corn. Low levels of the non-lethal compound, which causes vomiting, are often present in grain crops such as corn and wheat, but this year, the contamination is at a level that industry specialists haven’t seen for at least a decade. In one field that Bolton was farming on behalf of Middlesex County, vomitoxin levels were 25 parts per million — 25 times more than the Canadian Food Inspection Agency allows for pig feed. He’s found levels between five and nine parts per million in his own fields — about 45 minutes west of downtown London — where they are “usually zero or one,” he says.

Farmers whose corn is highly contaminated “are going to lose really badly,” says Art Schaafsma, a plant-agriculture professor at the University of Guelph’s Ridgetown campus. “And crop insurance may or may not help them out. It could be ‘make it or break it’ for many farmers.”

(Pig farmers will also be affected: they use the grain to feed their livestock and may have to pay a premium for higher-quality corn, says Peter Minnema, president of the Middlesex County Pork Producers.)

Outbreaks of vomitoxin — which is produced by a fungal infection — are common in temperate climates throughout the world, says David Miller, a chemistry professor at Carleton University. The toxin, also referred to as DON (deoxynivalenol), was identified by scientists only in the early 1970s. The last major outbreak in Canada, in 2016, hit durum wheat in the Prairies, causing major crop loss. Pasta prices rose 20 per cent as a result.

This time around, consumers are unlikely to feel an impact. Less than a fifth of Ontario-grown corn is used for human consumption; the majority is used as livestock feed or for ethanol production. In a given year, some vomitoxin does end up in food, according to the Canadian Food Inspection Agency, albeit at levels too low to make anyone ill. (In recent years, just one food recall has involved vomitoxin.)

“Health Canada has determined that corn flour and corn-based foods are very low contributors to Canadians’ overall dietary exposure,” Geoffroy Legault-Thivierge, a Health Canada spokesperson, writes in an email.

Schaafsma says the first inkling of the problem came as farmers scouted their crops in late July and early August as the corn flowered. When the harvest began in late September and October, tests conducted by grain elevators, ethanol plants, and millers acquiring the corn revealed the high levels, and some turned back deliveries.

Vomitoxin testing is relatively new. In 2006, when there was another bad outbreak, “they were just learning how to test at the ethanol plant,” says Schaafsma. “Years before that, they weren’t even thinking about testing. Now it’s commonplace.”

In late November, the federal and Ontario governments announced that they would assist farmers with the costs of vomitoxin tests and partner with Grain Farmers of Ontario in research aimed at reducing levels of the toxin in corn crops.

Since 2000, a specialized forecast service has alerted Ontario wheat farmers to conditions that could lead to the growth of the vomitoxin-producing fungal infection, which can then be reduced through the use of fungicides. A 2016 study, however, found that while using forecasting to introduce preventative measures is “functional,” it can take effort to convince farmers to use it, and the amount of field-specific data farmers need to gather for the modelling discourages use.

Ben Rosser, the agriculture ministry’s corn specialist, says there is interest within the agriculture industry in developing a weather-based forecast tool for corn. But Bolton questions the feasibility of such an idea: while there are only a few varieties of wheat that need to be monitored against weather and climate conditions throughout the province, he says, there are dozens of varieties of corn.

Miller notes that the industry has developed some coping strategies — as well as testing the crop, it will, if high levels of vomitoxin are found, sometimes dilute a supply of affected grains with a supply that has no or low levels of it. Bolton has come up with his own strategies to try to reduce the toxin — for example, screening the corn before drying (literally shaking it in a wire-mesh cone that resembles a sieve) to remove the elements, such as corn husks and plant parts, that are likely to have higher levels.

Right now, his best bet is to sell the crop to an ethanol plant for a price well below what it cost to produce. Anything is better than plowing the rest of the crop into the ground, he explains. This year’s cornfields will become next year’s food-grade soybean fields, and he can’t afford having stray corn seeds crowding them out. “So it's got to come off the field either way,” Bolton says.

This is one in a series of stories about issues affecting southwestern Ontario. It's brought to you with the assistance of faculty and students from Western University’s Faculty of Information and Media Studies.

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